Little more than a fortnight after a Massachusetts Institute of Technology proposal to store wind energy in a form of underwater pumped hydro comes news of a Norwegian company with a similar idea, according to Gigaom. The system proposed by Subhydro would consist of concrete tanks sited on the seabed at depths of between 400 and 800m.
‘Discharging’ the battery would consist of opening a port to allow seawater to rush into these empty tanks at many times atmospheric pressure, driving a turbine and generating electricity. Recharging is simply a matter of reversing the process, using cheaper non-peak or surplus energy to pump the water out of the containers. The company is claiming an 80% efficiency for the system, which they say is comparable to efficiencies achieved at conventional plants.